给定一个谓词公式，将其转换为等价的前束范式。用c++编写程序。求大神相助。挺难的
http://wenku.baidu.com/link?url=6POOVIvOia1cpT2RgZrG-9IdCKhfm5SaZrB9FF5pkrBp-COHLsjT94KY-x9p8YB5_9lgCyrNF8RHUw5b_c6cJQxGtPWMb408nrLwd5DE3m_